This invention relates to a surgical retractor instrument for use in maintaining a clear surgical field for access to the anterior vertebral region of the body.
Spine surgery, such as vertebral fusions, is common and is becoming more reliable as better methods are developed for stabilizing the back and improving bone grafts, for example, to repair disc injuries, vertebral fractures, and the effects of osteoarthritis. Many spine surgeries require an anterior approach, such as those for degenerative disc disease (both de novo and to correct failed prior back surgery), for infected discs, tumor removal and scoliosis (e.g., for excision, drainage, or decompression).
Anterior fusions are often preferable to posterior fusions because the bone surface area available for the fusion is considerably larger and any discs to be removed are more accessible. This makes the likelihood of successful fusion greater and the time required for the operation less, translating to less time that the patient is under general anesthesia. For example, since the introduction of threaded devices for Anterior Lumbar Interbody Fusion (ALIF), this procedure has become quite popular in the treatment of degenerative disc disease and chronic spinal instability as well as in failed posterior artlirodesis attempts. The procedure, however, is heavily dependent on the ability of the approach surgeon to provide exposure quickly and safely in view of a reported incidence of vascular injury as high as 15% (Baker et al, Spine 1993; 18:2227-2230) and a 2.3% incidence of retrograde ejaculation (Regan et al., Spine 1999; 24:402-11). The requirement of a direct anterior-posterior exposure for alignment of the devices has presented a significant challenge to provide a small incision and yet maintain the degree of safety necessary to prevent injury to the iliac vessels and the autonomic nerve plexus.
Generally, there are two anterior approaches for clearing a surgical field for the anterior lumbar region currently in use. One is the paramedian rectus splitting anterior retroperitoneal approach and the other is the lateral muscle splitting retroperitoneal approach. Both of these approaches have the disadvantage that they damage the muscles through which the surgeon must go to access the retroperitoneal space. Damaged muscle can lead to increased analgesic requirements during recovery, hernias, and loss of muscle function in the patient. Additionally, these approaches may require a large incision, leading to increased trauma to the skin, abdominal muscles, and internal structures. This can increase the subsequent pain for the patient, which requires additional post-operative management, while increasing recovery time. Procedures that entail or result in penetration of the peritoneum also lead to increased risk to the patient, for example, through damage to peritoneal organs, subsequent adhesions, infection, and the like.
Likewise, many surgical instruments are used once the field has been cleared to allow the spine surgeon access to the lumbar region. Retractors are used to secure the area open during the spine surgery. A variety of retractors and blades, and other implements such as Steinman pins, have been used for this purpose (see, e.g., U.S. Pat. Nos. 3,998,217, 4,813,401, 5,025,780, 5,052,373, 5,688,223, 5,728,046, 5,795,291,5,902,233, 5,944,658). While these retractors and implements help keep the area open and the tissue retracted, they suffer from several disadvantages. For example, standard retractor blades can slip out of place, or allow the peritoneum, peritoneal contents, nerves, vessels, or ureter to escape into the field of the surgery, risking injury to these structures. Hand-held retractors increase this risk. Pins are sometimes inserted into the vertebral body to hold back vessels and nerves, but they carry a great risk during deployment of the very damage the surgeon seeks to prevent. In lumbar region spine surgery, vascular injury, often perforation of the iliac vein and/or artery is the most common and severe complication. Other issues with the surgical instruments commonly used includes the size of the retractors, which may require a large incision in order to be placed correctly and to allow the spine surgeon a large enough field in which to work.
A published article entitled xe2x80x9cA Simple Retractor for Spinal Surgeryxe2x80x9d by G. Mosser Taylor, M.D., describes a retractor designed for use for posterior spinal surgery. However, use of a Taylor-type retractor could lead to potential damage to the neural and vascular structures that are being retracted in the case of anterior lumbar surgery. The tip of the retractor described by Taylor is too narrow, too tapered, too thin, and too long to be useful in anterior spinal surgery without the risk that the narrow relatively sharp tip would injure large vessels or nerves while being deployed.
U.S. Pat. No. 6,152,874 to Looney et al. describes a retractor used for coronary artery bypass surgery, but the design of this instrument would not be suitable for anterior lumbar surgery.
U.S. Pat. No. 5,971,920 to Nagel describes a retractor having spikes that turn inward which could prove dangerous when working near the Iliac arteries, the Iliac vein, and the sympathetic chain of nerves that run along the anterio-lateral border ofthe lumbar spine. Surfaces such as the spikes on the Nagel retractor are not used when working near these vital structures because damage of these structures can be life threatening.
Thus, a need exists for an instrument and anterior retroperitoneal approach that permits rapid surgical access to the desired lumbar area, permits a small incision, and is stable and safe during subsequent procedures.
The present invention provides a retractor blade and surgical access method that fulfill the need for rapid lumbar access, a small incision, and reduced risk of bleeding/accidental vascular injury, nerve injury, or ureter injury. The invention also provides a secure and stable open position even during bone routing, drilling, and screwing.
The invention features a retractor instrument for maintaining a clear surgical field for access to the anterior vertebrae region of the body. The retractor instrument comprises a handle portion and an elongated blade portion having a first end connected to the handle portion and a second end region spaced from the handle portion and shaped as a lip that curves in a direction away from the handle portion when the blade portion is in the operable configuration. The blade portion extends substantially along its entire length below an axis aligned with the handle and generally at an angle relative to the handle portion when the instrument is in an operable configuration. The lip portion of the blade takes up no more than about 20% of the blade length, preferably no more than about 15%, and most preferably no more than about 10%. The lip projects to a leading edge spaced less than about 2 cm from a plane defined by the blade portion immediately adjacent to the curvature of the lip. The lip has a width of at least about 1.75 cm., although in another embodiment the lip has a width of at least about 2 cm. The lip is of a shape and size sufficient to engage the lateral aspect of a vertebral body or vertebral disc when the blade portion is positioned adjacent to and substantially perpendicular to the vertebra and/or a disc. The lip of the blade has the advantage that it can securely engage the lateral aspect of a vertebral body, something that retractors not having this lip cannot do, and this secure engagement offers greatly improved retraction without tissue slipping into the surgical field. The lip also eliminates the need to have channels on the blade used to introduce sharp pins to secure the blade to the vertebral body. Those pins can actually cause damage if not secured properly. They also require wider exposure for proper placement and fail to provide lateral exposure for protection against vessel damage. Likewise, the lip itself does not have any sharp protrusions, which could cause tissue damage.
The blade of the retractor is preferably substantially flat in a rigid embodiment, or can be somewhat curved in a malleable embodiment, and the blade is preferably at an angle from about 80xc2x0 to 150xc2x0 to the handle when the retractor is in use. The angle is measured below an axis aligned with the handle. In one embodiment, the lip at the distal end of the blade is at least 0.5 cm long and curves at least about 0.15 cm from the plane of the blade, and is preferably roughened. Preferably, the lip has a radius of curvature of between about 1 cm and 3 cm and the curve of the lip extends between about 20xc2x0 and 50xc2x0 of the circle of curvature. The length of the blade portion is sufficient to reach the vertebral region from the anterior side of the body it is being used on. The width of the blade is preferably between about 0.5-2.5 inches, more preferably between about 1-2 inches, and most preferably between about 1 to about 1.5 inches. The width of the blade is important to protect against vessel damage, as in typical lumbar exposures, the space between the major vessels and the vertebral body is very limited and to use retractors with widths over about 2 inches risks stretching or otherwise damaging the vessels.
The invention also features a method of clearing an anterior lumbar region surgical field comprising making an incision on a body needing surgery that exposes the anterior rectus sheath of the left rectus muscle; cutting the anterior rectus sheath to expose the body of the rectus muscle; mobilizing the rectus muscle along its length by at least 3 cm in both directions from the site of the sheath incision, and retracting the rectus medially; cutting the posterior rectus sheath to expose the peritoneum; pushing aside the peritoneum and dissecting away any intervening tissues to expose the psoas muscle; mobilizing the ureter and the left iliac vessels so that they are retractable from the dissection field; and retracting the rectus muscle laterally, the peritoneum, ureter, vessels, and intervening tissues to provide a clear anterior lumbar region surgical field. This surgical procedure has the advantage that it does not damage the rectus muscle, nor does it perforate the peritoneum, so recovery for the patient is made much easier and faster, and the risk of complications is reduced.
Another feature of the invention is a method of exposing a selected area of the anterior lumbar region for a surgical procedure on that region comprising the steps in the above paragraph to expose the anterior lumbar region, and then retracting the rectus muscle laterally; inserting a retractor into the dissected field, the retractor comprising a handle portion and an elongated blade portion having a first end connected to the handle portion, the blade portion having a substantially flat configuration which generally extends at an angle relative to the handle, the blade portion having a second end spaced from the handle portion and shaped as a lip which curves in a direction away from the handle portion. The retractor is stabilized by engaging the lateral aspect of a vertebral body or disc with the lip of the retractor and retracting the tissues with the blade portion to expose the selected vertebral area. This method offers the advantages of secure retraction during further surgery, so that no blood vessels, nerves, or other structures are damaged by the retractor instrument, additional instruments, or accidental impact during the surgery.